How to kill White Noise & Burst Noise??

Discussion in 'The Projects Forum' started by canodw, Jul 1, 2011.

  1. canodw

    Thread Starter New Member

    Mar 29, 2011
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    Hi! Any suggestion on how to eliminate white noise and burst noise on audio circuit???
     
  2. t06afre

    AAC Fanatic!

    May 11, 2009
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    Hard to say. Can post your schematics, and some pictures of this noise
     
  3. canodw

    Thread Starter New Member

    Mar 29, 2011
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    here is my schematics. Audio_AMP_LIN and Audio_AMP_RIN are source of audio signals and headers are connected to the speaker. LD09 is DC supply 5volts. I will include here also the datasheet.
     
  4. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    If you are sure your voltage source in not responsible, then examine your grounding closely. That is a common way for noise to get into otherwise bulletproof designs.

    Also suspect your power supply filter caps. High resistance(from old or cheap caps) could also cause noise in outputs
     
  5. #12

    Expert

    Nov 30, 2010
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    This is a good design. If all else fails, you might have to consider that the chip has gone bad. I have actually seen a perfectly good amplifier get noisy because of the chip. They don't always quit completely.
     
  6. Audioguru

    New Member

    Dec 20, 2007
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    The datasheet shows pretty low noise when the gain is 2 but your gain is 10 and the datasheet shows then the noise level is 10 times (20dB) higher.

    Why is your schematic all spread out and an awful looking negative image? I fixed it.
     
  7. canodw

    Thread Starter New Member

    Mar 29, 2011
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    This is one of my findings during testing, when I disconnect the audio source the speaker don't produce any noise. But when I connect the line to the source without playing any music the speaker produces noise and when I play music the noise is not present. What do you think? Does the source (audio codec) creates noise?
     
  8. #12

    Expert

    Nov 30, 2010
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    I think you have just eliminated this circuit as being the problem.
     
  9. canodw

    Thread Starter New Member

    Mar 29, 2011
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    This is the noise at the speaker. Time = 0.1ms per div; .1V per div.. Please help me to cancel that noise.
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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    It sounds to me as if your audio source has an automatic gain control; when no music is playing, the gain is increased until you hear noise. When music starts playing, the gain is decreased so you no longer hear the noise.

    You need to figure out a way to disable that AGC circuit in the source. There is not a good way to eliminate the noise once it gets to your amplifier.
     
  11. canodw

    Thread Starter New Member

    Mar 29, 2011
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    Actually when I play music directly from the codec without amplifier the noise is not noticeable at the speaker (using large speaker), the audio sounds good. After I place an amplifier after codec there is a noise I need higher sound level thats why I put an amplifier. I think Audioguru is right.

    My audio codec doesn't have AGC, please help me to eliminate this noise. Many thanks.
     
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